On Fri, Apr 01, 2011 at 07:27:03PM +0200, Johannes Sixt wrote: > > OK, I've read up on thread-cancellation, and this code seems correct. > > pthread_cancel doesn't kill the thread right away, it just signals a > > cancellation-event, which is checked for at certain > > cancellation-points. A lot of the CRT functions are defined as > > cancellation points, so it'll be a matter for us Win32-guys to > > implement pthread_testcancel() and inject that into the > > function-wrappers of the CRT functions that are marked as > > cancellation-points. > > That's not going to happen. We cannot implement pthread_cancel() on Windows > because it would have to be able to interrupt blocking system calls. > (TerminateThread() is a no-no, given all the caveats about leaking system > resources that are mentioned in the manual.) > > [OK, "cannot" is a hard word. It is possible in some way, I'm sure. But that > would mean that we implement the equivalent of Cygwin or so...] > > But if I understand correctly what Jeff wrote so far, then the pthreaded case > happens to work - by chance or by design, we don't know (yet). Perhaps we can > get away with > > - /* no clue */ > + /* pthread_cancel(async->tid); not necessary */ Yeah, I think that would probably work, but I haven't had a chance yet to look deeper into why the pthread case doesn't hang. I have another case, too, which is that killing a "git push" in progress via signal will leave crufty child-processes around, still trying to push. One of these is the pack-objects sub-process, and the other is (in the no-pthreads case) the sideband demuxer. And obviously fixing that involves aborting the async process, too[1]. But we can again get away without pthread_cancel, because in the pthread case, we can just rely on the parent process dying to take down the thread. -Peff [1] Actually, my plan is to set up a signal/atexit handler to kill off children. Run-command callers can specify an option for "yes, this child should be killed if I am killed". Async callers will have it turned on automatically (since they won't even know if it's a subthread or a different process). So we won't actually be calling abort_async() anyway. -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html